PSI-4 Effects of Sorghum Inclusion in Lamb Diets on Apparent Total Tract Digestibility

Abstract

The objective of this experiment was to evaluate the effect of grain sorghum inclusion on the apparent total tract digestibility of lamb diets. This experiment utilized 24 Rambouillet lambs (46.1 ± 3.90 kg) that were previously used in a growth experiment. Animals were housed in 1 of 24 pens with 1 lamb per pen and 6 pens per treatment. Lambs were randomly assigned 1 of the 4 treatment diets prior to the growth experiment and remained on the same treatment for over the 10-d experimental period. Treatments included 1) Control (0% sorghum inclusion); 2) Sorg10 (10% corn substituted for sorghum); 3) Sorg20 (20% corn substituted for sorghum); and 4) Sorg30 (30% corn substituted for corn). Diets were ground using hammermill and titanium dioxide was added to the ground diet at 0.4% as an indigestible marker. Lambs were fed these diets for 7-d prior to fecal sample collection to allow for steady-state marker concentrations. Fecal grab samples were collected every 6 hours over the final 3 d and were composited by animal to represent each 2-hour period of a 24-hour cycle. Feed and composited fecal samples were analyzed for crude fat, crude protein, ADF, NDF, and ash. Data were analyzed using the LM function in R with a fixed effect of treatment. Significance was defined at P < 0.05 and means were separated using Tukey’s HSD where appropriate. Sorghum inclusion did not affect (P > 0.16) crude protein, crude fat, or acid detergent fiber digestibility. Neutral detergent fiber digestibility was reduced (P = 0.02) for animals consuming Sorg20 and Sorg30 compared with the control, and Sorg10 was intermediate. Organic matter digestibility tended to decrease (P = 0.08) with increasing sorghum inclusion. In conclusion, replacing corn with sorghum at levels up to 30% had minimal impact on nutrient digestibility in growing lambs.